The present invention relates in general to compound controlling or regulating systems and in particular to a method of and a device for self-diagnosis of the operation of a final setting member pertaining to one subsystem of a complex regulating system including additional additional subsystems, particularly for use in an internal combustion engine.
In many fields of technology it is conventional to determine magnitudes, values or positions by means of regulation or a control in which a regulator produces a variable, usually an electric signal having certain functional course which is applied to a final control or setting member. The regulator receives from the assigned regulating path input signals and processes the same in dependency on the resulting adjustment of the setting member. In this manner, the control behavior of the regulator depends on the evaluation of the measured actual values of the result of regulation.
In this arrangement it is conventional to provide, without major difficulties, a self-regulation or the so-called fail-safe circuits which detect electrical signals occurring at predetermined points and evaluate or check the same as to their correctness. Problems arise, however, when a diagnosis of the setting member itself is to be done without causing reaction in the regulating loop controlled by the setting member. To avoid this undesirable reaction it is necessary to inactivate the whole regulating system or, alternatively, to pick up the movement of the setting member by means of additional hardware component parts and evaluate these changes for the purposes of the diagnosis.
As known, a measure is always available to perform simply a diagnosis of the operation of a setting member at an inactivated regulating system in such a manner that the setting member under test is activated by the application of an external signal and then the setting member is monitored either visually or when that is not possible, by means of sensors or an auditory test.
The following considerations relate specifically to the conditions of diagnosis of a setting member of the so-called idling speed air charge regulator in internal combustion engines for which the present invention is particularly suitable. It will be understood, however, that this mention is not limited to the self-diagnosis of such air charge regulators for idling speed range of an engine, but can be applied in any kinds of controlling and regulating systems.
In the preferred application field of this invention, namely in regulating internal combustion engines or regulating systems which intensively affect the operation of a motor vehicle such as, for example, the systems known under the name Montronic or L-jetronic which are mostly controlled by microprocessors, then in such devices the self-diagnosis of participating components is increasingly felt as desirable and necessary. Testing of sensors in respective regulating systems is relatively simple inasmuch as signals produced by the sensors are applied as input magnitudes in the microprocessor and can be easily tested by means of a corresponding subroutine in the program. The testing of controlling or setting members controlled by the regulators or controlling devices however is substantially more expensive because from the inputs of the regulator at least feedbacks to the microprocessor would be necessary which would necessitate additional hardware component parts and wiring. Moreover, a mechanical failure or damage of the setting member itself (for example seizing of an air charge controlling element) cannot be recognized by these measures.